GPTLint is a linting tool that uses Large Language Models (LLMs) to enforce code quality rules. It employs a two-pass approach: a faster, cheaper LLM model identifies potential violations, and a more accurate, expensive model validates them to reduce false positives. The tool supports both built-in and custom rules defined in markdown files, caches results to avoid reprocessing unchanged files, and provides both a CLI and programmatic API. The architecture is modular, with separate components for configuration, rule parsing, linting, caching, and LLM abstraction.